The present invention relates in general to automatically positioned grille shutter systems for automotive vehicles for providing a cooling air flow into an engine compartment, and, more specifically, to joining multiple vane sets of an active grille shutter system in a manner that ensures complete closure of a slave vane set controlled via a linkage by a master vane set.
A vehicle grille located at a front of a vehicle provides an opening for the intake of fresh air into an engine compartment to assist the vehicle's cooling system in cooling the engine, transmission, and other components. The air flow passing through the grille may add aerodynamic drag when the vehicle is in motion. At higher speeds, the rate of the air flow and the resulting drag both increase. With a fixed grille opening that must provide sufficient air flow at all speeds, excess air flow and drag must be tolerated at higher speeds. Accordingly, active grille shutters have been developed to reduce or block air flow to match that needed for cooling purposes, thus reducing aerodynamic drag and improving fuel economy. Closed grille shutters can also provide a faster powertrain warm-up to improve fuel economy and performance of the passenger compartment heater.
A typical active grille shutter (AGS) includes an actuator that positions the grille shutters based on commands from a powertrain control module. The shutter may pivot through a range of about 90 degrees between fully closed and open positions, which may be typically commanded in fixed increments for a plurality of set shutter positions (e.g., 16 preset positions separated by about 6 degrees).
The actuator may be comprised of a smart motor that communicates with the powertrain control module over a multiplex bus, for example. The motor has an output shaft connected to a fixed grille shutter housing and to one of a plurality of movable vanes which are themselves linked together to form a vane set. When the actuator motor output shaft moves, it moves the attached vane which causes the other linked vanes to move together.
According to the grille styling used on certain vehicles, more than one grille opening may be employed—with each opening containing a respective vane set. The vane sets may usually be in approximate vertical alignment, but are not necessarily coplanar. In order to avoid the cost of placing separate actuators at each vane set, a linkage may be provided between the vane sets in a master/slave relationship. However, due to manufacturing tolerances it has been difficult to ensure that both of the linked vane sets become completely closed in synchronization. The actuator senses a resistance to movement when one vane set becomes fully closed. In response to the resistance, the motor shuts off. If one vane set remains partially open, the aerodynamic performance is reduced and undesirable noise may be created. Thus, it would be desirable to ensure full closure of each vane set despite any variations in the manufactured shapes or tolerances of the grille housing, vane sets, or linkage.
In using a single motor for controlling multiple vane sets, the motor torque requirements are increased, thereby necessitating a larger, more expensive motor. The highest motor torque required to be delivered by the motor typically corresponds to the act of opening the vane sets from a fully closed position during a time when the vehicle is traveling at high speed because of the need to overcome wind resistance. Additionally, a high motor torque may be required to open closed vanes that may be frozen in place by snow and ice in a cold climate. Thus, it would also be desirable to reduce the required motor torque when opening the closed vane sets.